1. Field of the Invention
Embodiments of the present invention generally relate to a tunnelling magnetoresistive (TMR) reader and a method for its manufacture.
2. Description of the Related Art
TMR readers are used in hard disk drives to read bits of data from the hard disk drive. An example of a TMR reader is shown in FIGS. 1A and 1B. The TMR reader 100 includes a first shield layer 102 and a sensor structure including a pinned layer 104, a barrier layer 106, a free layer 108 and a cap layer 110. The sensor structure may be fabricated by depositing all of the layers of the sensor structure and then depositing a diamond-like carbon (DLC) layer 112 thereover. A photoresist mask is then formed over the DLC layer. The DLC layer 112, as well as the layers of the sensor structure, are then patterned to form the sensor structure shown in FIG. 1A. During the etching, material from the various layers of the sensor structure may redeposit on the photoresist mask.
While the photoresist mask and DLC layer 112 are still present, an insulating layer 114 is deposited on top of the exposed first shield layer 102 and the sidewalls of the sensor structure. A hard bias layer 116 and a hard bias capping layer 118 are formed over the insulating layer 114. A second DLC layer 120 is formed over the exposed insulating layer 114, hard bias layer 116 and hard bias capping layer 118. The second DLC layer 120 and the first DLC layer 112 are used as chemical mechanical polishing (CMP) stop layers to protect the hard bias layer 116 and sensor structure during a CMP lift-off process that occurs later. The first and second DLC layers 112, 120 may have different thicknesses.
The DLC layers 112, 120 have several drawbacks. First, the first and second DLC layers 112, 120 are deposited in a tool that is separate from the tool used to deposit the hard bias capping layer 118 and the cap layer 110. Thus, depositing the DLC layers 112, 120 add process complication and increase the cost of manufacturing the TMR reader. Second, the DLC layers 112, 120 are typically removed using a reactive ion etching (RIE) process which adds process complication and cost. Third, the DLC layers 112, 120 may delaminate during the CMP process and thus could result in overpolishing of the TMR reader which leads to poor device performance. Finally, the different thicknesses of the DLC layers 112, 120 may make it difficult to achieve a truly planarized second shield layer 112 (See FIG. 1B) and thus result in a notch 124 in the second shield layer 122.